Masaaki Yuasa is, to my mind, the most interesting director working in animation today. Ever since his first feature, 2004's Mind Game, he has subjected himself to a nearly constant process of self-reinvention, with every one of his major projects shifting to a new style, genre, or most likely both. He's mostly worked in television, but he had a very phenomenal 2017 with two extremely well-received features. Both of those were released in the United States in 2018 by distributor GKIDS, and both are among the most stunning, even radical pieces of animation available on any screen of any size in the past twelve months.

The first one produced, though the second one released by GKIDS, The Night Is Short, Walk On Girl is also the more openly startling in pretty much every way. Stylistically and thematically, the film is a successor to Yuasa's 2010 television series The Tatami Galaxy, but this is no mere retread. It's a story of two nameless college students in Kyoto: an anxious boy who has a crush on a girl just starting to find her footing in the adult world. The film tells their stories using highly expressionistic animation, in which everything about the whole world bends itself around their subjective experiences of one incredible night that seems to stretch on for months...

The adolescent neuroticism that makes up the bulk of the film's story isn't new. What is – what is maybe, actually, genuinely unprecedented – is how Yuasa and his animators go about the business of depicting the characters' mental lives. Formally speaking, the film has two stylistic registers: flashbacks and fantasies are represented by bright, solid-color silhouettes that leave everything as featureless shapes, while the actual present looks more… well, we definitely can't call it "realistic".

Reality is a slippery thing in Night Is Short from the very start: this is a world of head colds that can pass throughout the entire city of Kyoto in the course of a few hours, of improvised guerilla theater getting interrupted by improvised guerilla musicals, of a pair of gods of romance getting thwarted in the plans by a petulant god of used books. It's an anything-goes sort of universe in which the only rational organizing principle is the boundless energy of being young and having a world to explore. The film is a celebration of so many things: drinking more than you should, poking around interesting stores, making a complete ass of yourself in front of a crush.

This celebration comes in large part through the freedom of the visuals, which shift between every color imaginable and warp the world itself to represent how the characters feel about each moment of their night (to name just one example the boy enters a spicy food eating contest at one point, with the size of his challenge literalized in the form of chunks of meat the size of his head, with the contestants reshaping their skulls around the food). It's a playful cartoon for grown-ups, evoking the girl's sense of discovery in its pure variety and the boy's constant discomfort in allowing the characters to be distorted and manipulated with no thought to continuity or plausibility. It's quite possibly the most ambitious animated film released this year, and certainly the most eager to take advantage of the evocative malleability of the medium.

Released just a bit less than a month later in 2017, but several months earlier in the U.S., Lu Over the Wall is less extravagantly weird. It is an ecological fairytale about a boy in a band helping to fight a corrupt developer with the help of a local ningyo (a kind of vampiric mermaid), with character designs that feel like the rounded, toyetic characters of much family-friendly animation. The style doesn't keep changing in the middle of the movie, or completely break down, though the characters are pretty damn rubbery and fluid, particularly the strange little mermaid child Lu herself.

A fan of something like Studio Ghibli (Princess Mononoke, Spirited Away) would be able to get their heads around this one pretty quickly. It's mostly devoted, at least in its first half, to Lu's delight in the world on land, and to celebrating the transporting powers of really good music. None of this is to say that Lu Over the Wall is Yuasa's "normal" movie. In its pointedly child-friendly way (the director's first project for which the phrase "child-friendly" at all applies), Lu is every bit as aggressive about breaking and rebuilding the animation medium as Night Is Short. Bodies are flexible things here; anybody who has seen enough 1920s or 1930s American cartoons, with their boneless protagonists, will be ready for the stretchiness of arms and legs being thrust towards the camera in amusingly grotesque exaggerations of depth.

To make this happen, the studio had to basically invent a new workflow. Lu is a combination of hand-drawn poses and automated Flash animation to create the frames in-between those poses. In so doing, Yuasa and company are trying to overcome the great limitation of Flash-style animation (which includes pretty much everything made on TV, for a start), its rigidity. Using software specifically designed to maintain the shape of objects in the service of contorting shapes is, technologically, a major revolution, and Lu represents a tremendous leap forward.

Of course, that's all backstage stuff, and only the most deeply obsessed of us could possibly care. The good news is that the movie is also an utter joy to watch, taking the basic stuff of "The Little Mermaid" and turning it into a brightly colored romp through a delightful world, with a character made up almost entirely out of innocent enthusiasm for our guide. It's a blissfully upbeat movie, one that assures us that the world is good and can be redeemed. Combine its infectious joy with its technical audacity, and the fact that this still only manages to be Yuasa's second-best film of the year speaks to just how impressive his 2017/'18 was – among the most creative, groundbreaking years ever witnessed by a single director.